Minimally invasive surgery is a new technique of surgical treatment using a slender laparoscopic or thoracoscopic and surgical instruments delivered into a patient's body through a small incision. It provides a range of advantages such as minimal invasion, slight pain, rapid recovery, short hospital stay and less hemorrhage. Despites so many advantages of minimally invasive surgery over the traditional open surgery, in the early days of this technique, operating space for the surgeon is limited for the smaller surgical incisions of body surface. Moreover, when a surgeon operates the surgical instruments under an endoscope, the manipulation directions of the surgical instruments is opposite to the desired ones as observed with the endoscope. Thus, difficulty of a surgery is increased and a surgeon can perform a minimally invasive surgical procedure dexterously after undergoing a long-term training.
With the development of robot-assisted minimally invasive surgery, minimally invasive surgical robots were provided as a good solution for the above issues. For example, with a teleoperation surgical robot, the surgeon can view two- or three-dimensional images of the patient's internal tissues captured by an endoscope and displayed on a display device of a master console. Also the images of the surgical site and two surgical instruments are displayed. And the surgeon can manipulate levers on the master console to teleoperation control manipulators and surgical instruments of the slave robot in a master-slave manner. With the assistance from the surgical robot, a minimally invasive surgical procedure can be accomplished with an enhanced operational accuracy, the same feelings and operations of the surgeon as in traditional open surgery which greatly reduce the operation complexity.
Currently, countries all over the world are actively doing research on surgical robotics, and a few products have been commercialized. A representative example of them is the da Vinci Surgical System developed by the Intuitive Surgical Inc., which is, however, bulky, complicated and expensive.
A prerequisite constraint for a surgical robot to perform a minimally invasive surgical procedure is to ensure that a surgical instrument mounted on the slave robotic manipulator is kept moving around a small incision on the patient's body during the operation, through which the surgical instrument comes into the patient's body. This requires the slave robotic manipulator to employ a remote-center-of-motion (RCM) mechanism.
Manipulator arrangements with such RCM mechanisms have been focus of research in the field of surgical robotics, but the existing solutions from the research have some deficiencies. For example, Chinese application No. CN103565529A describes a manipulator employing a double parallelogram mechanism, which provides that an end of an instrument mounted on the manipulator rotates around an RCM. This mechanism is, however, moveable with only one degree of freedom and the instrument is only allowed to pivot within a limited range. Chinese application No. CN101919739A describes another double parallelogram-base holder manipulator capable of moving in a larger space and providing an offset RCM. However, an instrument mounted on the manipulator is again only allowed to move around the RCM with one degree of freedom.
As noted above, both the above manipulators have an RCM at a distal end by a double parallelogram mechanism. However, each of these manipulators and the instrument mounted thereon is only able to move around the RCM with one degree of freedom, i.e., pivoting around the RCM. Adding a telescopic degree of freedom to the manipulators requires additional slidable components for enabling telescopic motion, that is to move toward or away from the RCM, which will expand the size of the manipulator and increase its design complexity.
Therefore, there is a need in the art for a manipulator with a telescopic movement with respect to an RCM and a pivotal movement around an RCM.